Baryta paper has long been used as photographic paper. In order to increase the speed of development, so-called water-resistant photographic paper obtained by coating both surfaces of base paper with a polyolefin was developed, and now accounts for a greater part of photographic papers used. Usually, the water-resistant photographic paper has a photographic emulsion layer on one surface thereof (generally a polyolefin layer containing an inorganic pigment such as titanium oxide, TiO.sub.2).
The other surface on which no emulsion layer is formed desirably has graphic properties and printability by ball-point pens, fountain pens, pencils, oily inks, waterbase inks, etc. for various purposes.
However, since the water-resistant photographic paper is coated with a polyolefin which is most generally polyethylene, its surface is hydrophobic and non-absorbent, and as such, it is difficult to write on it by pencils, fountain pens and the like. It further has the defect that the writing causes scratches, or by slight rubbing after writing, the letters may disappear or blur.
Heretofore, graphic properties, and printability have been imparted to a polyolefin layer by, for example, a method comprising roughening its surface by sand blasting, embossing, etc., and a method comprising roughening its surface by etching it with an acid. The polyolefin layer so treated still does not have entirely satisfactory graphic properties.
Various attempts have been made to overcome these defects. For example, a method has been disclosed comprising including an inorganic pigment having a size of from 1 to 40 microns in the polyolefin layer on the back of water resistant photographic paper as described in Japanese patent application (OPI) No. 43528/1980 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application); a method comprising forming a layer composed of a water-soluble polymer such as polyvinyl alcohol or carboxymethyl cellulose and aqueous silica sol on the polyolefin layer as described in Japanese Patent Publication No. 14884/1969, a method comprising forming a layer composed of a water-insoluble polymer emulsion such as a polyethylene emulsion and aqueous silica sol as described in Japanese Patent Publication No. 36565/75, and a method comprising forming a coated layer having hygroscopicity and containing a pigment such as clay as described in Japanese Laid-Open Utility Model Application No. 169426/1977.
These known methods, however, all have defects. For example, the method comprising including an inorganic pigment having a size of from 1 to 40 microns in the polyolefin resin layer has poor practicability because the photographic paper has reduced quality owing to cracking of the resin film and contamination caused by the pigment. Furthermore, with coated layers of conventional compositions the amount of coating should be increased to about 5 g/m.sup.2, and in some cases more than 10 g/m.sup.2, in order to obtain sufficient graphic properties, especially graphic properties by pencils, and the preparation of such coated layers has been restricted in many respects, for example, in regard to the drying step.
The qualitative defect is that in the step of development, these coated layers may peel off or dissolve, or after the development, the pigment comes off even by slight rubbing. Thus, these prior methods have failed to give products satisfying any of these properties.
On the other hand, in order to increase the resolving power of the water-resistant photographic paper, a method has been proposed in which a resin layer cured by electron beam irradiation is coated on both surfaces of base paper as a support, as described in Japanese Patent Application (OPI) Nos. 27257/1982 and 49946/1982. However, the resin layer coated on the back surface of the photographic paper support obtained by such a method is hydrophobic and non-absorbent, and as such, it is difficult to write on it with inks, ball-point pens, pencils, etc. Furthermore, it has the defect that during writing, scratchs may be caused, or by slight rubbing after writing, the writing may disappear or blur.